Iranian President Hassan Rohani, has warned U.S. President Donald Trump not to pull out of a landmark nuclear deal between Tehran and world powers, saying that the United States will face "severe consequences" if it violates the pact.

"I am telling those in the White House that if they do not live up to their commitments, the Iranian government will firmly react," Rohani said in a speech broadcast live on state television on April 24.

Trump has given the deal's European signatories a May 12 deadline to fix what he calls its "terrible flaws," threatening to effectively withdraw the United States by refusing to extend waivers on U.S. sanctions if they do not do so.

The Joint Comprehensive Plan of Action (JCPOA), which Iran signed with the United States, Russia, China, Britain, France, and Germany in 2015, put curbs on Iran's nuclear program in exchange for sanctions relief.

Aside from the United States, the other signatories of the agreement have all voiced support for the deal.

Speaking to a crowd of thousands in the northeastern city of Tabriz, Rohani said, "If anyone betrays the deal, they should know that they would face severe consequences. Iran is prepared for all possible situations."

French President Emmanuel Macron, a vocal proponent of the deal, is in the United States and is seeking to convince Trump not to torpedo the agreement.

Russian Foreign Minister Sergei Lavrov said on April 23 he had agreed with his Chinese counterpart that Moscow and Beijing would try to block any U.S. attempt to sabotage the nuclear deal.

At a UN nonproliferation conference in Geneva, Russia's delegate said on April 24 that his country and China have submitted a draft statement voicing "unwavering support" for the deal and hope the draft will receive broad backing at the meeting.

Vladimir Yermakov, the Russian Foreign Ministry's Director General for Nonproliferation and Arms Control, told the meeting that the Iran agreement was fragile and any attempt to change it it would impact on the global nonproliferation regime.

Yermakov's remarks came a day after Russian Foreign Minister Sergei Lavrov said he had agreed with his Chinese counterpart that Moscow and Beijing would try to block any U.S. attempt to sabotage the deal.

Iran has warned that it will revive and step up its nuclear program if the deal collapses.